gp_module_test.jl

#=
Objective:      Find minimum time vehicle control program
Terminal Set:   x (position)
                v (velocity)
                -1
Function Set:   +, -, *, DIV, GT, ABS
Cost:           Time to bring behicle to phase plane origin
                averaged over 20 random initial conditions
Gen. Limit:     50
Pop. Size:      500
Max Initial Tree Depth: 6
Init. Method:   Ramped half-and-half
Max. Tree depth: 17
X-Over Prob.:   0.9
Mutation prob.: 0
Number of elites: 2
Selection:      Tournament
=#
module GP
    function GT(a,b)
        """
        GT function to be used in AST
        """
        if a > b
            return 1
        else
            return -1
        end
    end

    function DIV(a,b)
        """
        Protected division used in AST
        """
        if abs(b) < 10.0^-10
            return 1
        else
            return a/b
        end
    end

    @eval function create_single_full_tree(depth, fs, ts)
        """
        Creates a single AST with full depth
        Inputs
            depth   Current depth of tree. Initially called from main() with max depth
            fs      Function Set - Array of allowed functions
            ts      Terminal Set - Array of allowed terminal values
        Output
            Full AST of typeof()==Expr
        """
        # If we are at the bottom
        if depth == 1
            # End of tree, return function with two terminal nodes
            return Expr(:call, fs[rand(1:length(fs))], ts[rand(1:length(ts))], ts[rand(1:length(ts))])
        else
            # Not end of expression, recurively go back through and create functions for each new node
            return Expr(:call, fs[rand(1:length(fs))], create_single_full_tree(depth-1, fs, ts), create_single_full_tree(depth-1, fs, ts))
        end
    end
end

function main()
    """
    Main function
    """
    # Define functional and terminal sets
    fs = [:+, :-, :DIV, :GT]
    ts = [:x, :v, -1]
    # Create the tree
    tst = GP.create_single_full_tree(4, fs, ts)
    #println(typeof(tst))
    #println(tst)
    #println(dump(tst))
    # If I comment these globals, eval cannot find x and v in the scope
    GP.x = 1
    GP.v = 1
    #eval(tst)
end
main()